Effect of Severe Plastic Deformation on Structure Refinement and Mechanical Properties of the Al-Zn-Mg-Fe-Ni Alloy

Abstract

This paper identifies the mechanisms of phase and structural transformations during severe plastic deformation by shearing under pressure (high-pressure torsion) of an Al-Zn-Mg-Fe-Ni-based aluminum alloy depending on different initial states of the material (an ingot after homogenizing annealing and a rod produced by radial-shear rolling). Scanning and transmission electron microscopy are used to determine the morphological and size characteristics of the structural constituents of the alloy after high-pressure torsion. It has been found that, irrespective of the history under high-pressure torsion, fragmentation and dynamic recrystallization results in a nanostructural alloy with a high microhardness of 2000 to 2600 MPa. Combined deformation processing (high-pressure torsion + radial-shear rolling) is shown to yield a nanocomposite reinforced with dispersed intermetallic phases of different origins, namely Al9FeNi eutectic aluminides and MgZn2, Al2Mg3Zn3, and Al3Zr secondary phases. The results of uniaxial tensile testing demonstrate good mechanical properties of the composite (ultimate tensile strength of 640 MPa, tensile yield strength of 628 MPa, and elongation of 5%).